In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or user equipments (UE), communicate via a Radio-Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to by a beam or a beam group which covers the area, with each service area or cell area being served by a radio-network node such as a radio-access node e.g. a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a “NodeB” or “eNodeB”. A service area or cell area is a geographical area where radio coverage is provided by the radio-network node. The radio-network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio-network node.
A Universal Mobile Telecommunications System (UMTS) is a third generation (3G) telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio-access network (UTRAN) is essentially a RAN using Wideband code-Division Multiple Access (WCDMA) and/or High-Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio-network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio-network controller (RNC) or a base-station controller (BSC), which supervises and coordinates various activities of the plural radio-network nodes connected thereto. This type of connection is sometimes referred to as a backhaul connection. The RNCs and BSCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS), also called a Fourth-Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network. The EPS comprises the Evolved Universal Terrestrial Radio-Access Network (E-UTRAN), also known as the Long-Term Evolution (LTE) radio-access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio-access network wherein the radio-network nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of an RNC are distributed between the radio-network nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio-network nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio-network nodes, this interface being denoted the X2 interface. EPS is the Evolved 3GPP Packet-Switched Domain.
Advanced Antenna Systems (AASs) is an area where technology has advanced significantly in recent years and where we also foresee a rapid technology development in the years to come. Hence it is natural to assume that AASs in general and massive Multiple Input Multiple Output (MIMO) transmission and reception in particular will be a cornerstone in a future Fifth-Generation (5G) system.
In relation to the Advanced Antenna Systems (AAS), beam-forming is becoming increasingly popular and capable and it is not only for transmission of data but also for transmission of control information. This is one motivation behind the (relatively) new control channel in Long-Term Evolution (LTE) known as Enhanced Physical Downlink Control Channel (ePDCCH). When the control channel is beam-formed, the cost of transmitting the overhead control information can be reduced due to the increased link budget provided by the additional antenna gain.
Automatic repeat-request (ARQ) is an error-control technique used in many wireless networks. With ARQ, a receiver of data transmissions sends Acknowledgements (ACKs) or Negative Acknowledgments (NACKs) to inform the transmitter of whether each message has been correctly received. Incorrectly received messages, as well as messages that aren't acknowledged at all, can then be re-transmitted.
Hybrid ARQ (HARQ) combines ARQ with forward error-correction (FEC) coding of the data messages, to improve the ability of the receiver to receive and correctly decode the transmitted messages. As with conventional ARQ, receivers employing HARQ send ACKs and NACKs, as appropriate, after each attempt to decode a message. These ACKs and NACKs are referred to as “HARQ feedback.”
For downlink HARQ transmissions in LTE today, HARQ feedback is sent from the wireless device, e.g. a User Equipment (UE) to the Network (NW) e.g. via a radio-network node on either Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel (PUSCH), depending on whether the wireless device has been scheduled for uplink PUSCH transmission or not. The NW such as the radio-network node may thereafter, on an individual HARQ-process basis, draw conclusions on whether the last HARQ reception for that process was successful or not Acknowledgement/Negative Acknowledgement (ACK/NACK) or even if the Downlink (DL) Assignment reception failed, i.e. the wireless device does not send any feedback also called Discontinuous Transmission (DTX).
The timing of the transmitted HARQ feedback in LTE is such that, for Frequency-Division Duplexing (FDD), the feedback from one HARQ Receive (RX) process is received in the Uplink (UL) in subframe n+4 if the corresponding DL transmission for that process was in subframe n, corresponding to 4 milliseconds (ms) in total. For Time-Division Duplexing (TDD), the delay from DL data transmission to UL feedback reception may be larger than four to cater for the half-duplex DL-UL split.
However, handling of a lot of feedback may be cumbersome and affect the performance of the wireless communication networks in a negative way.